Recent studies have shown that in addition to the well known retino-geniculostriate pathway, there are other parallel routes by which visual information can reach visual cortex. This new insight into the organization of mammalian visual systems assumes a special significance since it has been shown in man and other species that extrageniculate pathways and extrastriate cortex function importantly for vision even in the absence of striate cortex. We plan to focus on several important unresolved anatomical and physiological problems in an effort to better understand extrageniculate visual processing in the cat. Specifically, we propose to continue and extend our electrophysiological mapping studies in order to provide a detailed retinotopic map of the extrageniculate visual thalamus. We also propose a series of anatomical studies aimed at revealing detailed connectivity patterns among retinotopically defined cortical, thalamic, and other subcortical visual centers. These anatomical studies will utilize autoradiographic and HRP methods as well as recording methods to guide the placement of injections in thalamus and cortex. We believe this research will contribute importantly to our understanding of information flow through the mammalian visual system, and further that it will help to parcellate the cat extrageniculate visual thalamus into functional areas.